EXPERIMENTAL INVESTIGATION OF THE POINT OF INCEPTION EVOLUTION IN STEPPED CHANNEL

Abstract

Most prototype spillways operate at large discharges per unit width, and the water skims as a coherent stream over a pseudobottom formed by step edges. The nappe flow regime is divided into three sub-types, characterized by the formation or absence of hydraulic jumps on the bed of the stairs. The skimming flow regime is subdivided considering the geometry of the steps and the flow conditions that lead to different configurations of the flow fields near the steps. We have made an experimental approach in the laboratory of civil engineering at the University of Laghouat (Algeria), in three (03) models: model A (4cm x 7.5cm 4cmx) and model B (8cm x 7.5cm 8cmx), and the third model C size (12cm x 12 cm x 7.5 cm) developed "Plexiglas." Three slopes were studied in this experiment:  = 20 °, 30 ° and  =  = 45 ° for the three models, with flow rates ranging from q = 0.96 l / s / ml up to q = 33.02 l / s / ml. The purpose of this experimental study is the show the effect of rate flow, and the slope of channel in the evolution of the point of inception. Also, we proposed one empirical model for these evolutions cited.